A conventional resistor includes a side face electrode of four-layer structure, which is disclosed in Japanese Patent Laid-Open Publication No.03-80501.
As shown in FIG. 70, the resistor includes resistor layer 3 and a pair of squared-U-shaped edge electrodes 4. Resistor layer 3 bridges a pair of upper surface electrode films 2 disposed at respective ends on an upper surface of substrate 1, and is disposed slightly inward from side faces of substrate 1. The squared-U-shaped side face electrodes 4 are provided over respective side faces of substrate 1 and electrically connected with the pair of upper surface electrode films 2. Each of the side face electrodes 4 has a four-layer structure in including squared-U-shaped first metal film 5, second metal film 6, first metal plating film 7, and second metal plating film 8. Squared-U-shaped first metal film 5 is formed of one of a thin nickel-chromium film, thin titanium film, and thin chromium film as the lowermost layer, and is electrically connected to corresponding one of the upper surface electrode films 2. Second metal film 6 is formed of a thin copper film of low resistance overlying first metal film 5. First metal plating film 7 is formed of a nickel plated film overlying second metal film 6. Second metal plating film 8 is formed of one of a lead-tin plated film and a tin plated film overlying the first metal plating film 7.
The conventional resistor, since including second metal film 6 in the side face electrode 4 composed of a thin copper film of low resistance, has the first metal film 5 and the second metal film 6 do not transform easily into solid solution in their interface if this resistor is left in high humidity. Therefore, when moisture or the like is adsorbed in an interface between the thin copper film, i.e., the second metal film 6, and the lower layer of first metal film 5, the second metal film 6 be liable to exfoliate easily from the first metal film 5